code: def __len__(self):
      return self._data.size()[0]
  
file_path: nni/test/algo/compression/distillation/test_distil_label_patcher.py
imports: from __future__ import annotations
  import hashlib
  import pytest
  import torch
  from torch.utils.data import Dataset, DataLoader
  from nni.contrib.distillation.label_patcher import DistilLabelPatcher
  from nni.contrib.distillation.uid_dataset import IndexedDataset, HashedDataset, AugmentationDataset
  from ..assets.common import log_dir
label_desc: Use image node_id 2 for calling the DemoDataset obj's underlying member method code with example usage: obj.__len__() and returns: self